Vacuum may be used to operate or to assist in the operation of various devices of a vehicle. For example, vacuum may be used to assist a driver applying vehicle brakes, fuel vapor purging, heating and ventilation system actuation, and actuation of various valves such as a wastegate, a charge motion control valve (CMCV), etc. CMCVs may be coupled upstream of intake valves of engine cylinders in order to increase or decrease the charge motion of a corresponding cylinder, thereby increasing or decreasing the cylinder burn rate, respectively. Vacuum to actuate these valves may be obtained from an engine intake manifold in normally aspirated engines because the intake manifold pressure is often at a pressure lower than atmospheric pressure. When vacuum in the engine intake manifold is not sufficient, vacuum to actuate these valves may be received from a vacuum reservoir.
Diagnostic tests on vacuum actuated valves may be performed intermittently to identify degraded functionality. As an example, diagnostics may determine if a plate of the CMCV is stuck open (or stuck closed) based on a response of a position sensor coupled to the CMCV. If the position sensor does not indicate a change in position in response to an actuation command, the functionality of an actuator of the CMCV may be diagnosed as degraded. Accordingly, a diagnostic code may be flagged in a control system indicating a degraded actuator. However, diagnostic tests may incorrectly diagnose the vacuum actuator as degraded when adequate vacuum is not available to actuate the vacuum actuator. As such, incorrect diagnoses may result in false diagnostic codes being set which can lead to unnecessary testing and expenses. Overall, maintenance costs may increase leading to customer dissatisfaction.
The inventors herein have recognized the above issue and identified an approach to at least partly address the issue. In one example approach, a method is provided to diagnose degradation of a vacuum actuator. The method comprises indicating degradation of the vacuum actuator based on an estimate of flow of air into and out of a vacuum reservoir, the estimate based on flow of air generated via each of an aspirator in the intake system, an actuation of the vacuum actuator, and leakage during the actuation of the vacuum actuator. Thus, incorrect diagnoses of vacuum actuator degradation due to insufficient vacuum levels in the vacuum reservoir may be reduced.
For example, an engine may include one or more vacuum actuated CMCVs positioned in an intake passage downstream of an intake throttle and upstream of one or more intake valve(s) of cylinders. As such, the CMCVs may be actuated by a vacuum actuator that may source vacuum from either the intake manifold or a vacuum reservoir. During conditions when manifold vacuum is not adequate for actuating the CMCV(s), supplementary vacuum may be drawn from the vacuum reservoir. The vacuum reservoir may be fluidically coupled to each of the intake manifold of the engine, a suction port of an aspirator, and to one or more CMCVs. A total amount of vacuum fill in the vacuum reservoir may be estimated based on flow of air into the vacuum reservoir and flow of air out of the vacuum reservoir. Air may flow into the vacuum reservoir when actuating the CMCVs, and air may flow out of the vacuum reservoir towards the intake manifold and/or the suction port of the aspirator. If the amount of vacuum fill in the vacuum reservoir is estimated to be lower than a threshold level, adequate vacuum may not be available to actuate the CMCV(s). Accordingly, if actuation of the CMCV(s) does not produce a change in a position sensor coupled to the CMCV(s), the control system may not indicate that the CMCV is degraded. On the other hand, if the amount of vacuum fill in the vacuum reservoir is higher than a threshold level and actuation of the CMCV(s) does not produce a change in the position sensor, the CMCV(s) may be determined to be degraded.
In this way, degradation of a vacuum actuator may be more accurately determined based on estimating a total amount of vacuum fill in a vacuum reservoir coupled to the vacuum actuator. By determining that an available quantity of vacuum in the vacuum reservoir is lower than a desired quantity, non-responsiveness of the vacuum actuator may be attributed to a lack of vacuum in the vacuum reservoir. Accordingly, indications of vacuum actuator degradation during diagnostic routines may be diminished, particularly when vacuum fill in the vacuum reservoir is lower than desired. As such, diagnostic routines may be completed without a malfunction indicator light being actuated. This in turn may reduce needless and costly diagnostics, and unnecessary maintenance from being carried out.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.